WO2012053076A1 - Système d'évaluation de détérioration de catalyseur - Google Patents

Système d'évaluation de détérioration de catalyseur Download PDF

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Publication number
WO2012053076A1
WO2012053076A1 PCT/JP2010/068500 JP2010068500W WO2012053076A1 WO 2012053076 A1 WO2012053076 A1 WO 2012053076A1 JP 2010068500 W JP2010068500 W JP 2010068500W WO 2012053076 A1 WO2012053076 A1 WO 2012053076A1
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Prior art keywords
nox
fuel ratio
air
reducing agent
catalyst
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PCT/JP2010/068500
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English (en)
Japanese (ja)
Inventor
中村　好孝
徹 木所
裕 澤田
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トヨタ自動車株式会社
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Application filed by トヨタ自動車株式会社 filed Critical トヨタ自動車株式会社
Priority to PCT/JP2010/068500 priority Critical patent/WO2012053076A1/fr
Priority to US13/879,225 priority patent/US20130216436A1/en
Priority to EP10858632.2A priority patent/EP2631444B1/fr
Priority to JP2012539513A priority patent/JP5573958B2/ja
Publication of WO2012053076A1 publication Critical patent/WO2012053076A1/fr
Priority to US14/563,390 priority patent/US9459242B2/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
    • G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
    • G01N33/0037—NOx
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9495—Controlling the catalytic process
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F01N11/007—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M15/00—Testing of engines
    • G01M15/04—Testing internal-combustion engines
    • G01M15/10—Testing internal-combustion engines by monitoring exhaust gases or combustion flame
    • G01M15/102—Testing internal-combustion engines by monitoring exhaust gases or combustion flame by monitoring exhaust gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F01N2550/02—Catalytic activity of catalytic converters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F01N2550/03—Monitoring or diagnosing the deterioration of exhaust systems of sorbing activity of adsorbents or absorbents
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
    • F01N2900/1402—Exhaust gas composition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
    • F01N2900/1614—NOx amount trapped in catalyst
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • the present invention relates to a catalyst deterioration determination system.
  • NOx catalyst When the reduction control of NOx stored in the NOx storage reduction catalyst (hereinafter also simply referred to as NOx catalyst) is executed, and then the estimated value of the NOx storage amount in the NOx catalyst reaches the reference value, A technique for determining that the NOx catalyst is deteriorated when the NOx concentration detected by the NOx sensor downstream of the NOx catalyst is equal to or higher than a predetermined concentration is known (for example, see Patent Document 1).
  • the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique that can quickly and accurately determine the deterioration of the NOx storage reduction catalyst.
  • the catalyst deterioration determination system is: In a catalyst deterioration determination system for determining deterioration of an NOx storage reduction catalyst that is provided in an exhaust passage of an internal combustion engine and stores NOx and reduces the stored NOx by supplying a reducing agent, A supply device for changing the air-fuel ratio of the exhaust gas passing through the NOx storage reduction catalyst by supplying a reducing agent to the NOx storage reduction catalyst; A measuring device for measuring the NOx concentration in the exhaust downstream from the NOx storage reduction catalyst; A control device that adjusts the amount of reducing agent so that the air-fuel ratio of the exhaust gas becomes a lean air-fuel ratio when supplying the reducing agent from the supply device; Measured by the measurement device when NOx is occluded in the NOx storage reduction catalyst and the amount of reducing agent is adjusted by the control device so that the air-fuel ratio of the exhaust gas becomes a lean air-fuel ratio. A determination device for determining deterioration of the NOx storage reduction catalyst
  • the NOx storage reduction catalyst stores NOx when the air-fuel ratio is lean, and reduces the stored NOx when a reducing agent is present.
  • the supply device can supply the reducing agent to the NOx storage reduction catalyst.
  • the reducing agent may be supplied into the exhaust gas flowing through the exhaust passage or may be discharged from the internal combustion engine. Then, by supplying the reducing agent, the air-fuel ratio of the exhaust is lowered.
  • the NOx storage reduction catalyst deteriorates, NO 2 desorbed from the NOx storage reduction catalyst when supplying the reducing agent flows out downstream of the NOx catalyst without being reduced to N 2 . For this reason, the NOx concentration on the downstream side of the NOx storage reduction catalyst at the time of supplying the reducing agent becomes higher according to the degree of deterioration.
  • H 2 or HC may react with NO to generate NH 3 .
  • the measuring device NH 3 also results measured as NOx. For this reason, it cannot be determined whether the NOx concentration measured by the measuring device is the result of measuring NO 2 or the result of measuring NH 3 , for example. Therefore, if NH 3 is present, it is difficult to determine the deterioration of the NOx storage reduction catalyst based on the NOx concentration.
  • the control device prevents NH 3 from being generated by adjusting the amount of the reducing agent. That is, by controlling the amount of the reducing agent so that the air-fuel ratio of the exhaust gas becomes the lean air-fuel ratio, NH 3 is hardly generated, so the NOx concentration measured at this time is not affected by NH 3 Concentration. Since the NOx concentration at this time is correlated with the degree of deterioration of the NOx storage reduction catalyst, the deterioration of the NOx storage reduction catalyst can be determined based on the NOx concentration. Thus, the determination accuracy can be increased by performing the deterioration determination when not affected by NH 3 . In addition, since it is not necessary to wait until the NOx occlusion amount of the NOx storage reduction catalyst increases, it is possible to quickly determine deterioration.
  • the determination device can determine that the NOx storage reduction catalyst has deteriorated when the maximum value of the NOx concentration measured by the measurement device is equal to or greater than a threshold value.
  • a threshold is set as a value at which the maximum value of the NOx concentration becomes unacceptable. That is, the threshold value can be the lower limit value of the maximum value of the NOx concentration measured when the NOx storage reduction catalyst is deteriorated. Then, by comparing the maximum value of the NOx concentration measured by the measuring device with the threshold value, it is possible to determine whether or not the NOx storage reduction catalyst has deteriorated. When the maximum value of the NOx concentration is less than the threshold value, it is determined that the NOx storage reduction catalyst is normal. In this way, by performing the deterioration determination using the maximum value of the NOx concentration that is correlated with the degree of deterioration of the NOx storage reduction catalyst, the deterioration determination can be performed easily and accurately.
  • the determination device can determine that the NOx storage reduction catalyst is deteriorated when the integrated value of the NOx concentration measured by the measurement device is equal to or greater than a threshold value.
  • the integrated value of NOx concentration also increases according to the degree of deterioration of the NOx storage reduction catalyst.
  • the integrated value is obtained, for example, by adding the NOx concentration measured by the measuring device every predetermined time.
  • a threshold is set as a value at which this integrated value of NOx concentration becomes unacceptable. Then, it is possible to determine whether or not the NOx storage reduction catalyst is deteriorated by comparing the integrated value of the NOx concentration measured by the measuring device with a threshold value.
  • the threshold value can be a lower limit value of the integrated value of the NOx concentration measured when the NOx storage reduction catalyst is deteriorated.
  • the integrated value of NOx concentration is less than the threshold value, it is determined that the NOx storage reduction catalyst is normal.
  • the deterioration determination can be performed easily and accurately by performing the deterioration determination using the integrated value of the NOx concentration correlated with the degree of deterioration of the NOx storage reduction catalyst.
  • control device reduces the air-fuel ratio of the exhaust gas to a rich air-fuel ratio that reduces NOx before adjusting the amount of reducing agent so that the air-fuel ratio of the exhaust gas becomes a lean air-fuel ratio.
  • the dosage can be adjusted.
  • NO 2 flows out from the NOx storage reduction catalyst. If the reducing agent amount is adjusted so that the air-fuel ratio of the exhaust gas becomes a rich air-fuel ratio before that, NOx stored in the NOx storage reduction catalyst is reduced in advance, so the lean air-fuel ratio is set. The amount of NO 2 flowing out can be reduced. Further, since the stored amount of NOx does not immediately become zero even when the rich air-fuel ratio is achieved, NOx is also released as the lean air-fuel ratio thereafter.
  • the NOx occlusion amount is reduced by reducing NOx in advance, the NOx amount flowing out from the NOx storage reduction catalyst can be reduced when determining the deterioration of the NOx storage reduction catalyst. . Thereby, it is possible to suppress the release of NOx into the atmosphere.
  • the control device stops the supply of the reducing agent from the supply device after adjusting the amount of the reducing agent so that the air-fuel ratio of the exhaust gas becomes a rich air-fuel ratio for reducing NOx. Then, after a predetermined time has elapsed, the amount of reducing agent can be adjusted so that the air-fuel ratio of the exhaust gas becomes the lean air-fuel ratio.
  • NH 3 is released from the NOx storage reduction catalyst.
  • a predetermined time is set as a time until the influence of NH 3 disappears.
  • control device adjusts the amount of the reducing agent so that the air-fuel ratio of the exhaust gas becomes a lean air-fuel ratio, and at the air-fuel ratio at which NH 3 is not generated by the storage-reduction NOx catalyst and the storage
  • the air-fuel ratio can be made such that NO 2 is produced by the reduced NOx catalyst.
  • NH 3 hardly occurs when the air-fuel ratio is lean.
  • NO 2 is produced when the lean air-fuel ratio, the air-fuel ratio is too high, NO 2 is not generated almost. That is, when determining the deterioration of the NOx storage reduction catalyst, the accuracy of the deterioration determination is improved by adjusting the amount of reducing agent so that the air-fuel ratio is within a predetermined range in which NH 3 is not generated and NO 2 is generated. Can do.
  • FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its exhaust system according to the present embodiment.
  • the internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders.
  • the exhaust passage 2 is connected to the internal combustion engine 1.
  • An occlusion reduction type NOx catalyst 4 (hereinafter referred to as NOx catalyst 4) is provided in the middle of the exhaust passage 2.
  • the NOx catalyst 4 is constituted by, for example, using alumina (Al 2 O 3 ) as a carrier, and carrying, for example, barium (Ba) and platinum (Pt) on the carrier.
  • alumina Al 2 O 3
  • Pt platinum
  • This NOx catalyst 4 stores NOx in the exhaust when the oxygen concentration of the inflowing exhaust gas is high, and reduces the stored NOx when the oxygen concentration of the inflowing exhaust gas decreases and a reducing agent is present.
  • an injection valve 5 for injecting a reducing agent into the exhaust is attached to the exhaust passage 2 upstream of the NOx catalyst 4.
  • the injection valve 5 is opened by a signal from the ECU 10 described later, and injects the reducing agent into the exhaust.
  • the fuel (light oil) of the internal combustion engine 1 is used as the reducing agent, but the reducing agent is not limited thereto.
  • the fuel injected from the injection valve 5 into the exhaust passage 2 lowers the air-fuel ratio of the exhaust flowing from the upstream of the exhaust passage 2.
  • so-called rich spike control is performed in which the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 4 is decreased in a relatively short cycle by injecting fuel from the injection valve 5.
  • the amount of reducing agent injected from the injection valve 5 is determined based on, for example, the operating state of the internal combustion engine 1 (engine speed and fuel injection amount). The relationship among the amount of reducing agent, engine speed, and engine load can be mapped in advance.
  • an air-fuel ratio sensor may be attached to the exhaust passage 2 and the amount of reducing agent may be feedback controlled so that the air-fuel ratio detected by the air-fuel ratio sensor becomes a target value.
  • the injection valve 5 corresponds to the supply device in the present invention.
  • the reducing agent can also be supplied by discharging unburned fuel from the internal combustion engine 1. That is, an in-cylinder injection valve for injecting fuel into the cylinder is provided, and sub-injection (post-injection) for injecting fuel again during the expansion stroke or exhaust stroke after performing main injection from the in-cylinder injection valve is performed. Alternatively, by delaying the fuel injection timing from the in-cylinder injection valve, the gas containing a large amount of reducing agent can be discharged from the internal combustion engine 1.
  • an upstream NOx sensor 7 for measuring the NOx concentration in the exhaust is attached to the exhaust passage 2 upstream of the injection valve 5.
  • a downstream NOx sensor 8 that measures the NOx concentration in the exhaust and a temperature sensor 9 that measures the temperature of the exhaust are attached to the exhaust passage 2 downstream of the NOx catalyst 4.
  • the downstream NOx sensor 8 corresponds to the measuring device in the present invention.
  • the internal combustion engine 1 configured as described above is provided with an ECU 10 that is an electronic control unit for controlling the internal combustion engine 1.
  • the ECU 10 controls the operation state of the internal combustion engine 1 according to the operation conditions of the internal combustion engine 1 and the request of the driver.
  • the ECU 10 outputs an electric signal corresponding to the amount of depression of the accelerator pedal 11 by the driver to detect the engine load, and an accelerator position sensor 12 for detecting the engine speed. 13 are connected via electric wiring, and the output signals of these various sensors are input to the ECU 10.
  • the injection valve 5 is connected to the ECU 10 via electric wiring, and the ECU 10 controls the opening and closing timing of the injection valve 5.
  • the ECU 10 that adjusts the amount of reduction supplied from the injection valve 5 corresponds to the control device in the present invention.
  • the ECU 10 injects the reducing agent from the injection valve 5 within a range where the air-fuel ratio of the exhaust gas becomes lean, and determines the deterioration of the NOx catalyst 4 based on the NOx concentration detected by the downstream side NOx sensor 8 at this time.
  • the reason why the air-fuel ratio of the exhaust is made lean is that NH 3 flows out from the NOx catalyst 4 if it becomes rich. Since NH 3 is detected as NOx by the downstream NOx sensor 8, when the air-fuel ratio of the exhaust gas is rich, it cannot be determined whether NH 3 is detected or NO 2 is detected.
  • FIG. 2 is a diagram for explaining the NOx occlusion action in the NOx catalyst 4.
  • FIG. 3 is a view for explaining the NOx reduction action in the NOx catalyst 4.
  • the NOx catalyst 4 oxidizes NO with O 2 on Pt when the air-fuel ratio of the exhaust gas is lean, and stores it as Ba (NO 3 ) 2 in Ba.
  • Ba (NO 3 ) 2 is released as NO 2 and further reduced to N 2 on Pt.
  • the NOx catalyst 4 deteriorates, the surface area of Pt becomes small, so that the released NO 2 is difficult to be reduced to N 2 . Then, for example, part of NO 2 desorbed from Ba flows downstream from the NOx catalyst 4. The amount of NO 2 flowing downstream from the NOx catalyst 4 increases according to the degree of deterioration of the NOx catalyst 4. By detecting the NO 2 that this way flows out from the NOx catalyst 4 in the downstream side NOx sensor 8, it is possible to determine the deterioration of the NOx catalyst 4.
  • the NOx catalyst 4 reacts with NO and H 2 to generate NH 3 and H 2 O. Further, HC and NO react to generate NH 3 , H 2 O, and CO 2 .
  • the NH 3 thus generated reacts with O 2 in the downstream NOx sensor 8 and becomes NO, and is detected as NOx.
  • the downstream NOx sensor 8 detects NH 3 and NO 2 .
  • NH 3 is generated regardless of whether or not the NOx catalyst 4 is deteriorated. Therefore, when determining the deterioration of the NOx catalyst 4 based on the concentration of NO 2 downstream of the NOx catalyst 4, the NH 3 from being detected, even though the NOx catalyst 4 is not deteriorated There is a possibility that it is determined to be deteriorated. Therefore, in this embodiment, when determining the deterioration of the NOx catalyst 4, the amount of reducing agent is adjusted so that the air-fuel ratio of the exhaust gas becomes lean.
  • FIG. 4 is a diagram showing the relationship between the air-fuel ratio when the reducing agent is supplied and the detection value of the downstream NOx sensor.
  • NOx indicated by a solid line in FIG. 4 is the NOx concentration measured by the downstream NOx sensor 8.
  • NH 3 indicated by a one-dot chain line is an actual NH 3 concentration downstream of the NOx catalyst 4.
  • NO 2 indicated by a two-dot chain line is an actual NO 2 concentration downstream of the NOx catalyst 4.
  • the NOx catalyst 4 reacts with H 2 and HC of the reducing agent and NO to generate NH 3 .
  • the amount of NH 3 produced decreases as the air-fuel ratio increases and becomes zero near the stoichiometric air-fuel ratio.
  • NO 2 is easily reduced to N 2 , so the concentration of NO 2 is low, but not all NO 2 is reduced. That is, when the air-fuel ratio is rich, NH 3 and NO 2 are detected by the downstream NOx sensor 8, and the detected NOx concentration decreases as the air-fuel ratio increases.
  • the reducing agent is supplied so that the rich air-fuel ratio is close to the theoretical air-fuel ratio.
  • the amount of NO 2 and NH 3 produced is small, so that the detection value of the downstream NOx sensor 8 is minimized.
  • FIG. 5 is a time chart showing the transition of the injection signal and the NOx concentration detected by the downstream side NOx sensor 8 during the rich spike control according to this embodiment.
  • the injection signal is a signal output from the ECU 10 to the injection valve 5.
  • the injection valve 5 opens when the injection signal is ON to inject the reducing agent, and closes when the injection signal is OFF to stop the injection of the reducing agent. Then, when the reducing agent is injected, the air-fuel ratio of the exhaust gas flowing into the NOx catalyst 4 is lowered.
  • the air-fuel ratio of the exhaust gas can be adjusted by adjusting the injection period of the reducing agent.
  • normal rich spike control is performed.
  • This normal rich spike control is a control for reducing NOx stored in the NOx catalyst 4, and the rich air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio is set by making the opening time of the injection valve 5 relatively long. The Then, NH 3 and NOx flow out from the NOx catalyst 4, and the detection value of the downstream NOx sensor 8 increases.
  • NO 2 flows out while the NOx catalyst 4 is not reduced.
  • the normal rich spike control is performed in advance to reduce the storage amount of NOx, the amount of NOx flowing out from the NOx catalyst 4 when the deterioration of the NOx catalyst 4 is judged can be reduced.
  • the valve opening time of the injection valve 5 is made relatively short so that the air-fuel ratio of the exhaust gas becomes lean.
  • NO 2 is released according to the degree of deterioration of the NOx catalyst 4.
  • the deterioration of the NOx catalyst 4 can be determined based on the detection value of the downstream side NOx sensor 8 at this time. For example, if the maximum value of the NOx concentration detected by the downstream side NOx sensor 8 is equal to or greater than the threshold during the period indicated by B, it is determined that the NOx catalyst 4 has deteriorated.
  • the integrated value of the NOx concentration detected by the downstream NOx sensor 8 is equal to or greater than the threshold value, it may be determined that the NOx catalyst 4 has deteriorated. Note that the accuracy of deterioration determination can be increased by performing rich spike control a plurality of times during deterioration determination.
  • FIG. 6 is a flowchart showing a flow for determining the deterioration of the NOx catalyst 4. This routine is executed every predetermined period.
  • step S101 it is determined whether or not a precondition for determining deterioration of the NOx catalyst 4 is satisfied. For example, it is determined that the precondition is satisfied when the downstream NOx sensor 8 is normal. This determination can be performed by a known technique.
  • step S101 If an affirmative determination is made in step S101, the process proceeds to step S102, and if a negative determination is made, this routine is terminated.
  • step S102 it is determined whether the rich spike execution condition is satisfied.
  • the rich spike execution condition is a condition for performing normal rich spike control for reducing NOx stored in the NOx catalyst 4. For example, it is determined that the rich spike execution condition is satisfied when NOx of a predetermined amount or more is occluded in the NOx catalyst 4 and the temperature of the NOx catalyst 4 is a temperature suitable for NOx reduction. .
  • the amount of NOx stored in the NOx catalyst 4 is calculated based on the NOx concentration detected by the upstream NOx sensor 7.
  • the temperature of the NOx catalyst 4 is detected by a temperature sensor 9.
  • step S102 If an affirmative determination is made in step S102, the process proceeds to step S103, and if a negative determination is made, this routine is terminated.
  • step S103 normal rich spike control is executed. That is, the reducing agent is injected from the injection valve 5 so that the rich air-fuel ratio becomes close to the theoretical air-fuel ratio.
  • This rich spike control is performed for a time during which the stored amount of NOx can be reduced to some extent.
  • the execution time of this normal rich spike may be set in advance.
  • step S104 it is determined whether or not the elapsed time from the end of the normal rich spike control is equal to or longer than a predetermined time T.
  • the predetermined time T is a time until NH 3 released by the normal rich spike control is not detected by the downstream NOx sensor 8. That is, it is the time until the influence of NH 3 released by normal rich spike control disappears.
  • the elapsed time after the end of the normal rich spike control may be the elapsed time after the supply of the reducing agent from the injection valve 5 is stopped.
  • step S105 rich spike control for determining deterioration of the NOx catalyst 4 is performed. That is, rich spike control is performed within a range leaner than the stoichiometric air-fuel ratio. At this time, the air-fuel ratio is adjusted such that NH 3 is not generated and NO 2 is generated. For example, the amount of reducing agent may be adjusted so that the air-fuel ratio in the vicinity of the maximum NO 2 concentration in FIG. 4 is obtained.
  • the air / fuel ratio at which the detected value by the downstream side NOx sensor 8 is minimized may slightly deviate from the stoichiometric air / fuel ratio.
  • the amount of reducing agent is adjusted so that the air-fuel ratio on the side higher than the air-fuel ratio at which the detected value of the downstream NOx sensor 8 in FIG.
  • step S106 it is determined whether or not the maximum value of the NOx concentration detected by the downstream NOx sensor 8 is equal to or greater than a threshold value.
  • This threshold value is preset as a lower limit value of the maximum value of the NOx concentration detected when the NOx catalyst 4 is deteriorated.
  • step S106 If an affirmative determination is made in step S106, the process proceeds to step S107, and it is determined that the NOx catalyst 4 has deteriorated. On the other hand, if a negative determination is made in step S106, the process proceeds to step S108, and it is determined that the NOx catalyst 4 is normal.
  • the ECU 10 that processes step S106 to step S108 corresponds to the determination device according to the present invention.
  • the NOx catalyst 4 is more deteriorated as the maximum value of the NOx concentration detected by the downstream NOx sensor 8 when the rich spike control is performed within the lean range than the stoichiometric air-fuel ratio is larger. You may determine with a high degree. Similarly, it may be determined that the degree of deterioration of the NOx catalyst 4 is higher as the integrated value of the NOx concentration detected by the downstream NOx sensor 8 is larger.

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Abstract

Selon l'invention, l'évaluation de détérioration d'un catalyseur (1) de NOx de type rétention-réduction, s'effectue avec rapidité et exactitude. Un système d'évaluation de détérioration de catalyseur est équipé : d'un dispositif d'alimentation (5) qui assure l'alimentation en réducteur; d'un dispositif de mesure (8) qui mesure la concentration en NOx contenu dans l'échappement en aval par rapport au catalyseur (1); d'un dispositif de commande (10) qui ajuste la quantité de réducteur de sorte que le rapport air/carburant de l'échappement soit appauvri lors de l'alimentation en réducteur par le dispositif d'alimentation (5); et d'un dispositif d'évaluation (10) qui évalue la détérioration du catalyseur (1) sur la base de la concentration en NOx mesurée par le dispositif de mesure (8) lors de l'ajustage de la quantité de réducteur de sorte que le rapport air/carburant de l'échappement soit appauvri, c'est-à-dire lors de la rétention de NOx par le catalyseur (1).
PCT/JP2010/068500 2010-10-20 2010-10-20 Système d'évaluation de détérioration de catalyseur WO2012053076A1 (fr)

Priority Applications (5)

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PCT/JP2010/068500 WO2012053076A1 (fr) 2010-10-20 2010-10-20 Système d'évaluation de détérioration de catalyseur
US13/879,225 US20130216436A1 (en) 2010-10-20 2010-10-20 Catalyst deterioration judging system
EP10858632.2A EP2631444B1 (fr) 2010-10-20 2010-10-20 Système d'évaluation de détérioration de catalyseur
JP2012539513A JP5573958B2 (ja) 2010-10-20 2010-10-20 触媒劣化判定システム
US14/563,390 US9459242B2 (en) 2010-10-20 2014-12-08 Catalyst deterioration judging system

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US20130216436A1 (en) 2013-08-22
EP2631444A4 (fr) 2014-05-14
US20150090019A1 (en) 2015-04-02
EP2631444B1 (fr) 2016-01-13
EP2631444A1 (fr) 2013-08-28
US9459242B2 (en) 2016-10-04
JP5573958B2 (ja) 2014-08-20

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